Microelectronic devices, such as semiconductor devices and field emission displays, are generally fabricated on and/or in microelectronic workpieces using several different types of machines (“tools”). Many such machines have a single processing station that performs one or more procedures on the workpieces. Other processing machines have a plurality of processing stations that perform a series of different procedures on individual workpieces or batches of workpieces. In a typical fabrication process, one or more layers of conductive material are formed on the workpieces during the deposition stages. The workpieces are then typically subjected to etching and/or polishing procedures (i.e., planarization) to remove a portion of the deposited conductive layers for forming electrically isolated contacts and/or conductive lines.
Plating tools that plate metal or other materials on the workpieces are becoming an increasingly useful type of processing machine. Electroplating and electroless plating techniques can be used to deposit nickel, copper, solder, permalloy, gold, silver, platinum and other metals onto workpieces for forming blanket layers or patterned layers. A typical metal plating process involves depositing a seed layer onto the surface of the workpiece using chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating processes or other suitable methods. After forming the seed layer, a blanket layer or patterned layer of metal is plated on the workpiece by applying an appropriate electrical potential between the seed layer and an electrode in the presence of an electrolytic solution. Alternatively, the blanket layer can be applied to the workpiece using electroless processing techniques. In either process, the workpiece is then cleaned, etched and/or annealed in subsequent procedures before transferring the workpiece to another processing machine.
The foregoing operations are typically conducted within a single enclosed clean or “mini” environment in a processing tool. In a typical arrangement, a plurality of individual workpieces are brought to the tool in a portable container which defines another clean mini environment. A door of the container is placed flush against a door of the tool, and both doors are opened together to reduce the likelihood for introducing contaminants into the enclosure surrounding the tool. The workpieces are then moved into the enclosure.
Prior to processing the workpieces within the enclosure, the workpieces are identified by scanning a code or other identifying characteristic on the workpieces, for example with a bar code reader or other optical character recognition (OCR) system. The workpieces can also be aligned, for example, when the scan code or other identifying characteristic is positioned at a predetermined position relative to a recognizable feature of the workpiece, such as a notch or flat edge. This prealignment technique can also be used to precisely position the workpiece for subsequent processes that require the workpiece to have a specific orientation.
One existing arrangement for carrying out the prealigning and identification functions described above is to have a single robot retrieve workpieces one by one from the portable workpiece container, place the workpieces in a prealigner device, and then move the workpieces to downstream process chambers. Another existing approach is to have one robot remove the workpieces one by one from the container, deliver the workpieces one by one to a prealigner, then move the workpieces one by one to a transfer station. A second robot retrieves the workpieces from the transfer station, moves the workpieces among the appropriate processing stations, and returns the workpieces to the transfer station when the processes are complete. The first robot then moves the processed workpieces one by one to the original container or another container.
One drawback with the foregoing multi-robot approach is that the first robot may not operate efficiently because it must move each workpiece twice (once to the prealigner and once to the transfer station) before the workpiece is handed off to the second robot. Another drawback with this approach is that the first robot cannot operate entirely independently of the second robot because once the transfer station is occupied by a workpiece, the first robot cannot deliver another workpiece to the transfer station until the first workpiece is removed by the second robot.